Replacement Of Machines Research Articles

Pseudo-outbreak of Mycobacterium fortuitum due to contaminated ice machines

Background: An almost 4-fold increase from normal baseline levels in the isolation of Mycobacterium fortuitum from respiratory tract specimens was observed. The majority of these isolates were obtained from patients residing on 1 of 2 wards, prompting an epidemiologic investigation. Methods: In addition to patient specimens, environmental cultures were collected from various water sources on the 2 affected wards. Samples were also collected from uninvolved areas of the hospital. All specimens were cultured with use of a continuously monitored broth system for the isolation of mycobacteria. Results: The respiratory tracts of 19 patients were colonized by M fortuitum. Surveillance cultures obtained from uninvolved areas of the hospital were either negative for mycobacteria or were colonized by M avium complex or M gordonae. Two ice machines, servicing the affected areas each, were colonized by M fortuitum in multiple cultures. Conclusions: The M fortuitum pseudo-outbreak was due to contaminated ice machines located on each of the affected units. After removal and replacement of the ice machines, the pseudo-outbreak resolved. (Am J Infect Control 2002;30:184-6.)

A COMPUTER BASED MAINTENANCE MANAGEMENT SYSTEM WITH DECISION PROGRAMS

The development of a computer based maintenance management system is presented for industries using optimization models. The system which is capable of using optimization data and programs to schedule for maintenance or replacement of machines has been designed such that it enables the maintenance department control all jobs associated with plant maintenance and breakdown. It predicts the time to failure of designated plants and caters for the replacement analysis of some capital equipment. The system provides all the functions necessary for the control of maintenance spares. The system also provides complete details of the operation to be performed and parts to be used in a given maintenance job. The implementation of the system has been successfully carried out in a case study. Keywords: Maintenance, replacement, computerization, spares, inventory. [Global Jnl Engineering Res. Vol.1(1) 2002: 39-50]

Optimal repair of degrading computers under asymmetric information and incentive incompatibility

This paper presents the optimal repair policy of a firm's fault-tolerant computer system where asymmetric information and incentive incompatibility problems in allocating the computing resources are prevalent. Traditional maintenance optimization theory focuses on optimization models for repair, replacement, and inspection of machines (computers) subject to breakdowns or deterioration, without considering the allocation of such resources. Likewise, performance evaluation literature of fault-tolerant computers concentrates on deriving reliability and availability measures. This paper is a first attempt to jointly examine both the resource allocation and repair problems of a firm's fault-tolerant computer system. This paper presents the optimal repair policy of a firm's computer system in the presence of asymmetric information and incentive incompatibility. It applies the resource allocation model developed by Cheng et al. [Cheng, H. K., Freimer, M., Richmond, W., Sumita, U., Optimal allocation and backup of computer resources under asymmetric information and incentive incompatibility. European Journal of Operational Research, 1992, 91, 411–426] to analyze the impact of asymmetric information and incentive incompatibility on the repair policy of a firm's fault-tolerant computer system whose capacity degrades over time. A general methodology is presented for deriving the optimal repair policy for the firm's computer system by integrating the results from the resource allocation problem and the stochastic model describing the degrading capacity behavior of the computer system. The optimal repair policy is demonstrated via numerical results that offer useful insights. In particular, the conventional wisdom of having a largest asymptotic expected computer capacity does not guarantee a desirable long-run minimum cost to the organization.

Strategic planning in manufacturing systems — AHP application to an equipment replacement decision

The analytical hierarchy process (AHP) has been investigated with respect to its compatibility with strategic planning in manufacturing. Specifically, it was examined in its ability to support decisions in incrementing an organization towards higher levels of automation/technology in their manufacturing processes. The replacement of several milling machines at Deutsche Aerospace Airbus, Germany, required the development of a strategic plan to address both automation in manufacturing systems and machinery replacement. The objective of this research was to develop/explore different planning alternatives ranging from extending the life of existing machinery to total replacement with a new manufacturing system and to evaluate these alternatives through economical and technological criteria. Quantitative (financial and technological) and qualitative (intangible) benefits of investments in new manufacturing systems were considered using the AHP with the aid of AutoMan, a microcomputer program for multiple criteria decision making.

Implementing flexible automation: A multiple criteria decision making approach

This paper presents a multiple objective mixed integer linear programming model for the multiperiod flexible automation selection problem. The model includes five objectives, designed to address financial aspects, flexibility, firm disruption, and group homogeneity of new modules. The proposed model incorporates several types of flexibility. An interactive multiple criteria solution procedure is used to obtain an approximate optimal solution, based on a decision maker's implicit and unknown value function. The solution provides schedule for replacement of current machines, implementation of new modules, and production plans capitalizing on flexibility during transition and subsequent periods. A numerical example is provided to illustrate the approach. The optimal solution is then contrasted with that of a single-objective model.

The replacement of machines in a serially dependent multi-machine production system

In this paper a heuristic procedure is developed for solving the problem of planning machine replacements for a serially dependent production system. Given a finite planning horizon, the decision-maker wishes to decide (1) which periods, if any, that the entire production system must be shut down in order to make replacements, and (2) what specific machine or machines in the system should be scheduled for replacement during each of these downtime periods. The problem involves a balancing of costs. If the production system is brought down to make one or more replacements a fixed downtime cost is incurred; this cost is independent of the machines replaced during the downtime. In addition, other fixed coats are incurred for each of the machines replaced. Our motivation for scheduling these replacements is to realize lower variable costs for operating the machines. The variable operating costs are assumed to increase as the age or vintage of the machines increases. An optimal replacement policy is one in whic...

Impact of technological change on labor productivity in U.S. coal mines—Evidence from time series and cross sectional data

In this paper, we examine the impact of technological change (TC) on labor productivity in underground and surface mines. TC in the underground mines is the replacement of continuous machines for conventional miners between 1951 and 1970 and the recent penetration of longwall machines. In surface mines, TC consists of substitution of medium and large sized power shovels and draglines (PS&DLs) for smaller counterparts. Impact of these capital stocks vis-à-vis such other explanatory variables as seam thickness or strip ratio, utilization of capacity, captive vs non-captive mines, skilled labor, large sized mines and a dummy variable for coal mine regulations, on labor productivity is analysed by regressing the effects of these explanatory variables on labor productivity. The data used for the analysis include time series, as well as cross section data for mines in the Energy Information Administration's tapes for 1977. The analysis shows that adoption of newer technologies increases labor productivity in both mine types. Other variables that explain increases in productivity are increased seam thickness (in underground mines), exploitation of non-captive mines, use of skilled labor, and use of large mines. The variables explaining decreases in productivity are increased use of semi-skilled labor, strip ratio (in surface mines), mine accidents, and coal mine regulations.

Theoretical and Empirical Problems in Modeling Optimal Replacement of Farm Machines

Research on the optimal replacement problem has emphasized specification of the theoretically appropriate criterion. Today, the most commonly applied replacement decision theory for machinery assumes that the owner will replace each older machine, “defender,” with an identical new machine, “challenger,” in accordance with long-run cost minimizing or profit maximizing criteria (i.e., wealth maximization). Perrin (p. 60) summarizes the cost minimization criterion which should be applied: “A machine should be kept another period if the marginal costs of retaining it … are less than the ‘average’ periodic costs of a replacement machine.” As Chisholm noted, this criterion is “deceptively simple.” Support for Chisholm's observation is evidenced throughout the literature, because acceptance and use of an appropriate criterion has come about slowly.

Regional technological change in US coal mines: 1951–1976

This paper analyses technological change in coal mines in five regions—the Northern and Southern Appalachians, the Rocky Mountains, the Interior and Gulf and Northern Great Plains. Such an analysis can help identify the regions that are growth centres of the future and those that are the declining centres, so that an orderly transfer of manpower and resources from the latter to the former can be brought about efficiently and expeditiously. Section 2 deals with changes in production profiles, over time, of the regions by dividing coal mines into underground and surface mines. It concludes that the Appalachian regions are the declining regions with lower labour productivity and that the Northern Great Plains, with its increasing labour productivity, is the expanding region. Technological changes (TC) in underground mines consist of replacement of conventional mining machines by the continuous miners and the replacement of the latter by the long-wall machines. The TC in the surface mines is the substitution of intermediate- and large-sized power shovels and draglines (PS and Ds) for their smaller size counterparts. Section 3 presents a methodology of S-shaped growth curves. Section 4 reports empirical results for growth rates of adoption of the newer techniques across regions. These results reveal that the Northern Great Plains region is not absorbing the manpower and resources released by the Appalachian regions so that there are shortages in the former in the face of unemployment in the latter. There is, therefore, an opportunity for the declining Appalachian regions to inform their surplus manpower and resources about the growth centre in the north and prepare them for relocation, retraining and readjustment to the changes.

Economics of technological change in U.S. coal mines, 1951–1975

This paper deals with theoretical and empirical analysis of the economics of technological change (TC) in coal mines for the period 1951–1975. It divides the coal mines into underground and surface mines. The TC in underground mines is that of replacement of conventional mining machines with continuous machines and longwall techniques, whereas that in the surface mines is the adoption of power shovels and draglines with larger sized buckets and dippers (Section 2). The theoretical model (Section 3) is a dynamic S-shaped curve called a Gompertz function, and the empirical estimates (Section 4) are given in terms of regression equations based on the theory. The estimates of growth rates of adoption are based on demand or output of coal, as well as on capital and labor costs in the mines. Policy implications (Section 5) for increased market penetration of the technologies refer to government planners in terms of measures to help reduce capital costs by means of tax credit etc. and to labor unions for reductions in labor costs by wage restraint.

Economic interpretation of models for the replacement of machines

The purpose of this article is to give an economic interpretation of results derived from mathematical replacement models. It is based on results found in the literature. The conclusion is that the moment of replacement is always determined by the equality of marginal replacement costs to the marginal costs of postponed replacement. This extension gives the models practical applicability by providing an exact decision criterion and a concrete interpretation. In other words: practical decisions are given a theoretical foundation.

組立成功率

This paper proposes an index of the stochastic estimation in assembly, "the probability of success in assembly", which is computed as a function of the distribution of disturbances to the assembly operation and of the characteristics in the machine structure, and presents its applications. In order to estimate a plug insertion process by an assembly machine with elastic structure, the positioning error, the angle error of parts and the clearance between parts are chosen as the disturbances. Its application gives these merits as follows: (1) As the probability of success estimates the accuracy of positioning or chucking "quantitatively", the unreasonable requirement of accuracy can be eliminated from the design of machines. (2) To estimate the availability of the equipments without constructing and driving them actually allows the frequent replacement of machines, that is eagerly required in small batch production system. (3) As the index of the accuracy of part dimensions, the probability of success can decide whether the matching assembly should be adopted or not and benefit the total manufacturing system.

Organization of the repair and replacement of automatic glass-molding machines

Organization of the repair and replacement of automatic glass-molding machines

Oligopole et progrès technique

Oligopoly and technical progress Analysis of the rules adopted in practice for the replacement of machines brings out the essential role played in this field by the rate of profit considered by the firm to be normal. The most recent enquiries show that this profit rate is notably higher than elsewhere in those firms which benefit from a monopolistic situation. It must, therefore, be admitted that the development of monopolies brings about an increase in the level of profitability demanded from new investments, an increase which slows down technical progress. The opposite view, expressed by Josef Schumpeter, rests upon a superficial view of the historical evolution of capitalism. It is possible that, at the beginning of the 20 th. century, the creation of monopolies did make it possible to resist the general decline of the rate of profit, a stagnation factor. But after a brief period of euphory, monopoly capitalism cannot fail to be threatened once again with stagnation.